The two fimbriae associated adhesins of Bacteroides loescheii which mediate the coaggregations with Streptococcus sanguis 34 or Actinomyces israelii PK14 are presently being characterized. The S. sanguis 34 specific adhesin appears to be a hexamer composed of 6 - 75kD subunits. Moderate quantities of this protein have been purified to homogeneity by conventional and affinity chromatography. Its N-terminal amino acid sequence and amino acid composition has been determined and its pI has been estimated. Purification and characterization of the A. israelii PK14 adhesin is also underway. A method of purify the fimbriae that carry these adhesins has been developed, these larger structures appear to be complex helices composed of four intertwined protein strands. The carbohydrate receptor on S. sanguis H1 which is recognized by an adhesin on Capnocytophaga ochracea has been isolated from streptococcal cell walls, purified to homogeneity and characterized by NMR and mass spectroscopy. It was shown to be composed of a repeating hexasaccharide composed of rham-rham-gal-gal-gal-glu linked through phosphodiester groups. Monclonal antibodies specific for an afimbriate adhesin on the outer membrane of Capnocytophaga gingivalis DR2001 have been used to identify and localize this lectin like protein. The adhesin mediates the coaggregation by C. gingivalis and strains of Actinomyces israelii. The adhesins are not found uniformly over the surface of the cell and appear to be preferentially located at the poles of the cell. Like B. loescehii, there are relatively few adhesin molecules per cell, between 190 and 300.